Method of preventing the shrinkage of puffed tobacco and product obtained thereby



United States Patent 3,409,027 METHOD OF PREVENTING THE SHRINKAGE-OF PUFFED TOBACCO AND PRODUCT OBTAINED THEREBY Roger Zygmunt de la Burd, Richmond, Va., assignor to Philip Morris Incorporated, New York, N.Y., a corporation of Virginia No Drawing. Filed Dec. 17, 1965, Ser. No. 514,698

5 Claims. (Cl. 131-140) ABSTRACT OF THE DISCLOSURE This disclosure relates to a method for arresting tobacco stem shrinkage in the mesophyllic cells or the tendency of pulled or expanded stems to revert to their normal size, which method involves adjusting to a moisture content of from about 8% to about 16%, then expanding or pulling the stems, moisturizing the outer portion of the stems with Water at room temperature or steam by exposure thereto for from 5 to 60 seconds, passing said moistened stems between heated spreading means maintained at a temperature of at least 100 C. and so positioned as to provide a gap of about 0.02 to 0.05 inch and to exert a pressure differential on the stem thus ellecting separation of the mesophyll and epidermis from the lignified xylem without collapsing the pulled stem structure of the mesophyll cells but while partly powderizing the dry lignified fractions. Stems so treated are incorporated into tobacco sheet and used as cigarette filllers.

This invention relates to a tobacco product and method of preparing the same. More particularly, the present invention relates to an improved tobacco product which is adapted to be included in reconstituted tobacco sheets and to a method for preparing the same.

It has been found that tobacco stems and large veins may be incorporated into a tobacco sheet which is then chopped and used as cigarette fillers. Improvements have been suggested in the art which involve expanding or pulling the stems by some means to give them characteristics like that of natural tobacco leaf. Forexample, US. Patent #2,739,599 issued to Abbott and US. Patent #2,344,106 issued to Reed disclose such pulling. Copending applications Nos. 514,667, 514,699, and 516,112, entitled, Tobacco Stems Pulled by Radiant Energy and Method for Preparing Same, Tobacco Stems Pulled by Microwave Energy and Method for Preparing Same and Combined Air Separation and Pulling Process, respectively, and filed of even date herewith disclose improved pulling methods.

Pulled tobacco stems, however, can exhibit a serious drawback which has not been appreciated in the prior art. It has been found that if puffed stems are allowed to stand for even a short period of time after treatment, they begin to revert to their normal size; that is, they shrink from the expanded or pulled dimensions and ultimately attain the dimensions of unpulled stems. Thus, if no further treatment is afforded these pulled stems, many of the advantages obtainable from pulling are negated. It is therefore an object of the invention disclosed herein to treat the stems soon after pulling to retain their desirable properties.

Microscopic studies of unpulled and pulled tobacco stems have shown that it is the mesophyllic cells which pull when the stems are treated by any of the processes outlined above. The mesophyllic cells are those bridging the space between the lignified xylem and the stern epidermis. In like manner, it is these cells of the mesophyll which contribute to the shrinkage of pulled stems if they are allowed to stand after pulling with no further treatment.

3,409,021 1C6 Patented Nov. 5, 196

According to the present invention, it has been found that stem shrinkage can be arrested in the mesophyllic cells by detaching the mesophyll from the epidermis and xylem and spreading the stem open. When spread, a flattened structure approximately 0.02 to 0.4 inch thick is obtained. This flattened structure may be converted into filler for tobacco products such as cigarettes and compare favorably with natural tobacco leaf. The process may be adapted to production line techniques.

. Several advantages are realized by spreading puffed tobacco stems immediately after pulling in accordance with the present invention. The pulled stem does not shrink back to its smaller, unpulled volume. It therefore has a filling power greatly in excess of that of unpulled stems or pulled stems which have been allowed to shrink. That is, less filler by weight is required per cigarette if pulled stems are spread according to the instant invention.

The present invention comprises the following steps.

Tobacco stems, of the bright or burley variety, but preferably of the bright variety are equilibrated to a moisture content of from about 8% to about 16%, preferably 12%. The stems are then expanded or pulled by any of the means named above.

Immediately after pulling, the stems are conditioned with water or steam to moisten the outer portion of the stem. The optimum conditioning occurs when the stems are exposed to steam for from about 2 seconds to about 60 seconds, preferably 20 seconds. Alternatively, they may be soaked in water at room temperature for about 30 seconds.

The moistened stems are then passed through rollers or spreaders whose gaps are sufiicient to deform the epidermis and hence separate it from the mesophyll and xylem. The minimum usable gap width is determined by the distance at which air is forced out of the pulled stems and they collapse. It has been found that the minimum gap distance which will ellect separation without collapse of the expanded stern structure is .02 inch while the maximum gap distance is .05 inch. Greater gap widths will not separate the epidermis from the xylem and mesophyll in the normal pulled stem. Optimum gap width is a function of the size and type of stem being pulled and varies between the limits given.

An alternate method for spreading the outer moistened pulled stems is to pass them through a set of cogged rollers or spreads, the stern axes being parallel to the roller axes. The gap distance between the outermost faces of the cogs is .02 to .05 inch. As the cog faces pass into proximity with each other, they exert a pressure dillerential on the pulled stems and detach the mesophyll and epidermis from the l-ignin. The detached mesophyll easily slips through the cog faces without being subjected to a force which would flatten or crush the expanded cells while the dry lignified fractions are partly powderized.

The spreaders, cogged or smooth, must be heated, either by some internal heating means adapted to maintain a temperature of at least C. at the surface or by directing a jet of steam upon the spreader faces as they revolve. If moistened stems are passed through cold rollers, they shrink while dry stems are susceptible to excessive dusting or deterioration.

It is believed that the spreading serves to stabilize puffed stems by separating the expanded or pulled mesophyll and epidermis from the lignin which otherwise acts somewhat like a coiled spring to return the stem to its former unpulled dimensions.

The following examples are illustrative:

Example 1 Samples containing 2 lbs. each of bright stems were measured in a cylinder which has been graduated for this purpose. Triplicate samples were puffed by radiant heat, by low-heat vacuum, and by microwave energy. The radiant heat puffing was accomplished by exposing the stems to two 1000 watt G.E. Type T quartz lamps for 35 seconds at a distance of 3 inches. The low-heat vacuum pufiing was effected by treating the stems for 15 minutes at 150 C. in a Freas laboratory vacuum chamber at 25 mm. Hg. The microwave putting was achieved by exposing the stems in a Raytheon Mark V magnetron oven at a distance of 7 inches for 35 seconds. The increase in volume immediately after puffing was measured in the graduated cylinder and the stems were stored at 24 C. and 70% R.H. and at 24 C. and 60% R.H. The decrease in volume due to shrinkage of the expanded structure was again measured in the graduated cylinder at various intervals.

The results are illustrated in Tables 1 and 2.

TABLE 1 [Volume change of puffed stems. (24 C. and 70% relative humidity)] Volume (ml.) Time (Days) Low Heat Radiantly Control Pufled Pufied (Not Stems Stems Pufied) Immediately After Putting 1,100 800 600 1 650 600 600 2 675 625 600 7 050 650 600 TABLE 2 [Volume change of pufled stems. (24 C. and 60% relative humidity)] Volume (ml.) Time (Days) Low Heat Radiantly Control Pufied Puiied (Not Stems Stems Pufied) Immediately After Pufling 1, 050 1,000 1 l, 000 750 500 2 -Q 750 700 500 7 650 650 500 After initial shrinkage, the puffed stems occupied at most 35% more volume and had approximately 35% lower density than the unpuffed stems at all relative humidities examined. The decrease in volume occurred during the early period of moisture equilibration and the examination of this phenomenon led to the development of a practical method to prevent the loss in volume discussed in Examples 2, 3, and 4.

Example 2 Ten pounds of -45 bright tobacco, stem-in-leaf was puffed by ultra high frequency microwave energy in a Mark V microwave oven as described in Example 1. The dried material was conditioned with steam for 15 seconds to moisten the outer surface of the stern and lamina. The whole leaf was then spread at different distances between the spreaders. The gap distances employed were from .020"-.050". The strip was then cut into filler at 35 cuts/inch. By the proper adjustment of the distance between the spreaders, leaf containing puffed stem was processed without damaging the leaf portion.

The behavior of cut filler on storage at 24 C. and 70% R.H. and at 24 C. and 60% RH. was then measured in 500 ml. samples by the technique described in Example 1. Volume measurements were taken at various intervals over a period of 7 days. There was no decrease in the volume of the filler. In fact, at 24 C. and 70% RH, there was an increase in volume with time due to the re laxing of the cut puffed filler. Cigarettes made from the filler also showed that the puffed structure of stems was stable on storage and no apparent shrinkage occurred.

Example 3 Seventy pounds of bright stems, puffed by radiant heat, low-heat vacuum, and ultra high frequency microwave energy as described in Example 1 were moistened in steam for 20 seconds and processed while hot through a 4 set of spreaders set .019" apart and .03" apart. The resulting pressed pufied stems were somewhat thicker than the distance between the spreaders. The moisturizing technique was critical since high moisture and temperatures below C. caused the stems to shrink. The puffed stems were moisturized immediately and spread before any appreciable shrinkage occurred. The volume changes are illustrated in Tables 3 and 4.

It was apparent that once the stems had been spread at the given gap widths, they no longer shrank. In fact, it was observed that some of the rolled stems increased in volume when stored at the proper conditions of temperature and moisture. This was due to the relaxing of the rolled puffed structures. If, on the other hand, stems were rolled conventionally or spread at distances below 0.02, the pressure was too great. The expanded cell structure collapsed.

Example 4 One hundred pounds of stems puffed by radiant heat, low-heat vacuum, and ultra high frequency microwave energy as described in Example 1 were conditioned to 6.7% moisture in a Guardite chamber. The stems were immediately spread to yield a flattened stem of approximately 0.030 inch thickness. The spread stems did not lose volume when conditioned to 24% moisture and could be cut into filler suitable for making cigarettes.

Example 5 Twenty pounds of radiantly pufied stems were spread on large factory rollers used to crush stems in the conventional manner existing in the industry. The spreading equipment was adjusted to a gap distance of 0.020". The stems were steamed in polyethylene bags and immediately spread. The rollers themselves were steamed before the stems were put through, and were in eifect converted into spreaders, in accordance with the invention, by the application of heat and the correct setting of the gap width. The spread stems had a desirable appearance in that they were not crushed to the hard, shiny, nonabsorbent slime that usually results from the typical crushing of tobacco stems. The spread puffed stems still retained an absorbent spongy structure which retained the advantages resulting from puffing. These spread puifed stems were blended with tobacco leaf and cut into filler judged suitable for cigarette making.

I claim:

1. A method for producing a filler for a tobacco product which comprises puffing tobacco stems, moisturizing the outer portion of said stems, passing said stems between heated spreading means such that essentially opposing mechanical forces are applied about a gap of from about .02 inch to about .05 inch, so as to deform the stern and cause the epidermis to separate from the xylem and mesophyll.

2. The method of claim 1 wherein the stems are mois turized by subjecting them to live steam for from about 5-60 seconds.

3. The method of claim 1 wherein the stems are moisturized by immersing them in water at room temperature from 5-60 seconds.

4. The method of claim 1 wherein the spreading means are maintained at a temperature of at least 100 C.

5. A filler for a tobacco product comprising puffed tobacco stems in which the epidermis has been separated from the mesophyll and xylem by moisturing the outer portion of said stems, passing said stems between heated spreading means such that essentially opposing forces are applied about a gap of from about .02 inch to about .05 inch.

References Cited UNITED STATES PATENTS 2,344,106 3/1944 Reed. 2,739,599 3/1956 Abbott.

MELVIN D. REIN, Primary Examiner. 

